The present invention relates to the field of data and signal communications and communication systems. More particularly, the invention relates to network elements used to facilitate network communication.
A high level of detailed knowledge regarding network devices and protocols is presumed of practitioners in the art. This application presumes familiarity with commonly used network terminology and protocols. For additional background information, the reader is referred to the well-known RFC (Request for Comments) publications of the Internet Engineering Task Force (IETF), as well as the networking standards published by standards bodies such as the IEEE and the International Standards Organization (ISO). This application presumes familiarity with various well-known communications protocols such as ATM (Asynchronous Transfer Mode) and SONET (Synchronous Optical Network). For more information about SONET, the reader is referred to coassigned patent application Ser. No. 09/020,954, now U.S. Pat. No. 6,046,833, filed Feb. 9, 1998, entitled METHOD AND APPARATUS FOR OPERATION, PROTECTION, AND RESTORATION OF HETEROGENEOUS OPTICAL COMMUNICATION NETWORKS, which is incorporated herein by reference for all purposes.
Layered Network Protocols
Modem networks operate according to a layered network protocol suite. One published model for a typical protocol suite is known as the International Standards Organization (ISO) Open Systems Interconnection (OSI) reference model. In the OSI model, networking functions are divided into roughly seven layers, which from the lowest layer to the highest layer may be referred to as: (1) the physical layer, (2) the data link layer, (3) the network layer, (4) the transport layer, (5) the session layer, (6) the presentation layer, and (7) the application layer. In some situations, Layer 1 (the physical layer) includes a number of sublayers. These sublayers may include a second, mostly independent, generally high-speed, network with an independent layered protocol suite. Sublayer communication can include, for example, public data networks provided by telephone companies or by internetwork service providers. One typical example of a sublayer is a high-speed optical network, such as SONET, that can be used to provide distant physical layer links to a subscriber network. Another technology used for sublayer communications is ATM. A sublayer network that provides physical layer connections to network elements in another network is sometimes referred to as a subnetwork.
A set of standard interfaces is implicit between different network protocols operating at different layers. Typically, a particular network element handles traffic primarily at one layer or a subset of layers. For example, layer 3 traffic, consisting of Internet Protocol (IP) packets and other layer 3 packets, is generally handled by NEs referred to as routers, while layer 2 packets (or frames) are generally handled by NEs referred to as bridges. However, in some implementations, the functions of these separate NEs have been blended, such that some NEs may function partially as routers and partially as bridges.
An important concept in a layered network protocol suite is the ideal of layer independence. Layer independence implies that protocols and devices at one layer may operate with a variety of different protocols and devices operating at higher or lower layers without detailed knowledge about operation of those other layers. Generally, each layer is responsible for monitoring traffic and performance at its own layer (when performance is monitored at all) and there is little or no direct communication between layers of performance or configuration information.
Determining Channel Operation without Examining Channel Data
In some situations it may be disadvantageous for a network element (NE), or group of NEs, to directly monitor its own performance. One such situation arises in optical networks, where it is desirable to route some or all of an optical signal through an NE without examining that signal, as described as a particular embodiment in application Ser. No. 09/020,954, now U.S. Pat. No. 6,046,833. Other such situations might arise in present or future designs of ATM-type or sublayers or other sublayer technology, where faster or cheaper service can be provided at a sublayer if other NEs can be used by the sublayer to detect transmission problems.
In optical networks, it is known for optical NEs using wave division multiplexing (WDM) to indirectly monitor the performance of a data channel by monitoring the performance of a different wavelength (like the optical supervisory channel) on the same optical cable and from that to infer performance of the data channel. This is an imperfect method for ensuring the accuracy of the data channel itself, however. Another known optical method is for a transmitting optical NE to impress a low frequency signal onto an data signal. The receiving NE can then monitor the low frequency signal to infer the data optical signal quality. This, however, does require some sampling of the data wavelength and also requires additional transmission and detection circuitry for the optical NEs.
It has been proposed to develop new protocols for an NE such as an optical NE to communicate with NEs in other layers to determine the performance of the optical traffic. However, developing such protocols is time consuming and difficult given the large variety of higher layer NEs that may communicate data with the optical layer and a practical means for doing so has not yet been developed.
Another alternative solution is intervention from a human operator with access, either via multiple management stations or an integrated management system, to the status of the different network layers. The operator would then use information from a management station(s) to inform the optical or ATM sublayer NE that there is a problem on a particular connection. However, in many situations, this solution is slow and expensive.
What is needed is a method and apparatus allowing network devices in one group or operating at one layer to configure themselves or be configured in response to traffic conditions determined from a different layer and without intervention from a separate management station.
What is further needed is such a method that does not require the development of new protocols for exchanging configuration information between layers. What is further needed is a method and apparatus in an optical network allowing optical NEs to detect and respond to optical channel difficulties without having to directly sample or monitor channel data signals.
What is further needed is a method and system allowing a network layer capable of reconfiguring itself to provide services or connections to a different layer to infer connection performance and make configuration decisions without incurring the burden of analyzing a data payload channel for control information.
The present invention in one general aspect provides a method and system for dynamically re-configuring portions of a network and for checking network connections using out-of-band monitoring. In various embodiments, the invention includes a mechanism for a network element (NE) in a first group of NEs to coordinate its configuration and behavior with an NE in a second group, where the first NE is not participating in the coordination protocols of the second group. In an embodiment with important advantages, the invention uses existing standard network management protocols and an installed base of management agents in the second group to effect this coordination. In another important aspect, the invention provides a mechanism for an NE or a group of NEs to determine the performance of a communication channel passing through that NE without examining a data signal in that communication channel.
In one embodiment, the invention utilizes an agent associated with an NE and capable of communicating operating parameters. There is a large installed base of such agents, typically in layer 3 (L3) network devices (such as routers). These agents are generally intended for communication with network management stations that report network operations to a human user. In prior art systems, existing installed agents are intended to facilitate configuration of the NE in which they are installed or with which they are associated, generally through intervention of a human network manager. According to an embodiment of the invention, a first NE, possibly one operating at a different network layer or a different network or subnetwork, uses the agents to learn about the success or failure of data handled by a second NE and to thereby infer the performance of the first NE. The first NE may then take configuration actions on itself or may use the agent in the second NE to affect the configuration of the second NE. This action may include such things as rerouting data from failed or overloaded communication channels, changing priorities, changing path costs, or establishing backup paths for heavily used communications channels.
One area of particular interest for the invention is in sublayer communications using optical NEs. In such networks, it is desirable for the optical NEs to be able to detect channel defects without examining the optical signal in the channel, and the present invention provides a mechanism for these NEs to detect trouble or failure in optical channels indirectly from other NEs.
A related area of particular interest for the invention is in communications where an intelligent NE attempts to provide traffic redirection or other reconfiguration based on the operation of communications in a different group of NEs. In some prior art networks, an intelligent NE accesses the data payload channel (or payload signal) to determine control information. IP routers and SONET ADMs, for example, receive and transmit payload traffic and analyze received payload signals in order to identify control information. This control information, sent and received on the same channel as the payload, allows the Routers/ADMs to infer the health of the attached network and make appropriate decisions. In prior art systems, a lower network layer can also determine the identity of the source of the signal or the NE at the other end of the direct connection layer by examining and analyzing the payload signal or channel. The SONET protocol, for instances, includes embedded overhead bytes in the data stream that are intended to be detected and acted upon by SONET-layer devices.
With the advent of higher speed network transmissions (such as optical transmissions) and optical layers with intelligence, the burden of analyzing a payload channel for control information, relative to the forwarding of the payload itself, has increased. The burden of analysis is further increased in optical devices that can carry a multiplicity of optical payload data formats.
Previously, a method and system using a standard network management protocol to exchange information between network layers to coordinate activities of a particular network layer was described. The present invention extends that approach to provide additional functions of detecting node failure and rerouting signals without examining a payload channel. In one embodiment, the present invention avoids building into lower layer or other layer NEs an ability to interpret or analyze a payload data signal, because control information intended for analysis by the other layer devices is not embedded in the same channel with payload data.
One function an intelligent network layer according to the invention can provide is to redirect communications away from a failed network node device to a backup device for that node. The intelligent network layer is initially informed of the desired connectivity and the planned backup connectivity and provides the connection between the primary nodes. As discussed in the above referenced application, and herein, an intelligent layer according to the invention makes queries to other-layer network devices in order to detect a failure of the primary device and provide the backup connectivity. The present invention has the advantage over prior art approaches in that it neither requires changes to the operation of other-layer network equipment, such as the ability to parse new protocols, nor does it require analyzing and parsing the payload signal.
The invention will be explained with respect to specific embodiments, but it will be clear to those of skill in the art that the invention may be deployed in many alternative network configurations. The invention may also be deployed for configuration of network devices between different layers than the layers specifically described herein. For the sake of clarity, the invention will be described in terms of specific exemplary networks. It is inherent in the art that networks can be highly variable in the arrangement and configuration of different components. These examples should therefore been taken as illustrations; and not seen as limiting the invention. It is also inherent in the art that network systems are illustrated at a particular layer of abstraction, with many devices and details omitted.